Instructables posted a guide to creating a plumbers'-crack detector, using a
LilyPad Arduino »10/25/08 9:00am 10/25/08 9:00am controller, a vibrating motor, and a photoresistor to measure how much light is beaming into your crack. When the photoresistor comes uncovered, the motor starts to vibrate, letting you know that your "coin slot" is exposed…